Fragmentation of relativistic nuclei in peripheral interactions ... - JINR

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Fragmentation of relativistic nuclei in peripheral interactions ... - JINR

Fragmentation of relativistic nuclei inperipheral interactions in nucleartrack emulsionDenis Artemenkov,JINR (for the BECQUEREL collaboration)


IntroductionNuclear beams of energy higher than 1 A GeV arerecognized as a modern tool used for the study of thestructure of atomic nuclei*. Among the variety of nuclearinteractions the peripheral dissociation beams a uniquelycomplete information about the excited states above particledecay thresholds. The peripheral dissociation is revealed asa narrow jet of relativistic fragments the summary chargeof which is close to the charge of the primary nucleus. Inspite of the relativistic velocity of motion the internalvelocities in the jet are non-relativistic.*T. Aumann, Eur. Phys. J. A, 26, 441(2005).2


BECQUEREL at the JINR Nuclotron is devoted systematic exploration ofclustering features of light stable and radioactive nuclei.http://nucloserv.jinr.ruEmulsion layerThe fragmentation of a large variety of light nuclei was investigated using theemulsions exposed to few A GeV nuclear beams at JINR Nuclotron. A nucleartrack emulsion is used to explore the fragmentation of the relativistic nuclei.3


0.5 μm resolution, identification of charges and H&He isotopesThe emulsion technique provides a record spatial resolution and allows one toobserve the 3D images of peripheral collisions. The analysis of the relativisticfragmentation of neutron-deficient isotopes has special advantages owing to alarger fraction of observable nucleons.4


Collision of anucleus of theMg-Si group(Z~12-14)**H.L. Bradt and B. Peters, Phys. Rev. 77 (1950).5


The 12 С3 and 16 O4 fragmentation at the energy of 3.65 A GeV wasstudied at JINR Synchrophasotron* .12C3 , 3.65 A GeV(PAVICOM image)*V.V. Belaga et al., Phys. At. Nucl., vol. 58 (1995).6


The 16 О4 fragmentation were investigated using a large amount ofinformation (641 events). An analysis of the angular correlations gaveevidence that the angular momentum was transferred to the systems offragments and that the cascade decays via 8 Be and 12 C nuclei werenonessential*.16О4 , 3.65 A GeV (PAVICOM image)*F.A. Avetyan et al., Phys. At. Nucl., vol. 59 (1996).7


CountsFragmentation of relativistic 9 Be nuclei at 1.2 A GeVThe beam of relativistic 9 Be nuclei was obtained in the 10 B 9 Befragmentation reaction with polyethylene target (JINR Nuclotron).Z=5 (primary 10 B mark)800600400Z=2Z=3Z=4 ( 9 Be)9Be fraction in the beam:67 2 %*Found: 362 events of9Be 2 fragmentationAngular measurementsaccuracy not worse then4.4 10 -3 rad.2000100 150 200 250 300 350channels*today at 12.50: P.A. Rukoyatkin «Secondary fragment beams for studies of lightnuclei structure using the emulsion technique at the LHEP facilities». 8


9Be“white” starsIV9Bestars with target proton recoil (g-particle)stars with heavy fragment of target nucleus (b-particle)9


Opening angle Θ between two α fragments for 9 Be→2α9BeΘ=4.4±0.2, 10 -3 rad.σ Θ =2.1±0.2, 10 -3 rad.0-10.5 10.5-15.015.0-45.045.0-114.0=27.0±0.6, 10 -3 rad.σ Θ =5.9±0.6, 10 -3 rad.10


Polar angles θ of fragments for 9 Be→2ασ 1=(6.8 0.4) 10 -3 rad.σ 2=(16.4 0.8) 10 -3 rad.9Beθf ( )22Ni12 N2i2 exp2 2 events with opening angles Θ (0, 10.5) 10 -3 rad.;events with opening angles Θ (10.5, 114.0) 10 -3 rad.11


MQ222Mm22E1 2mE 2p1p 2cos( 12)120 + , 8 Be( 92 keV, 6.8 keV)Θ (0, 10.5), 10 -3 rad.2 + , 8 Be( 2.9 MeV, 1. 5 MeV )Θ (15.0, 45.0), 10 -3 rad..12


The target dependence of 9 Be2 fragmentationAgBr H CNO+AgBrn g=0n b=0n g=1n b=0n g=0n b=3n g=0n b=4n g=0n b=5n g=0n b=6n h>2(ng0)…Numberof events176 33 9 9 2 1 43 … 3621 12 3 3Wti R0 AtAi1.17 , R01.452fmTarget P, % W ( 9 Be-Em),nucleus(BR-2), %H 9 2 10.4CNO+AgBr 917 89.613


The results comparison of 9 Ве2α, 12 С3α, 16 О4αfragmentation in nuclear track emulsionParameter9Be (BR-2),9Be2α12С (BR-2),12С3α12С (BR-2+Pb),12С3α16О (BR-2),16О4α2P Tnumber ofevents1/ 2, MeVc362 44 72 641148 674 4, Θ(0,10.5) mrad.,156 9, Θ(15.0,45.0) mrad.,177 8, Θ(10.5, 114.0) mrad.192 10 161 6 167 42P* T1/ 2, MeV/c98 420 2, Θ(0,10.5) mrad.,105 9, Θ(15.0,45.0) mrad.,130 9, Θ(10.5, 114.0) mrad.141 7 130 8 145 3kT, MeV 2.60.11, Θ(0,10.5) mrad.,3.0, Θ(15.0, 45.0) mrad.,4.5, Θ(10.5, 114.0) mrad.4.0 3.4 3.7* kT 2 AFAP*2TAAFmN*F.A. Avetyan, et al., Phys. At. Nucl. 59 (1996)14


…summary1) In the first time the properties of 9 Be like 2 +n system is studied inperipheral fragmentation in nuclear track emulsion with relativisticenergies, using the Nuclotron of JINR.2) The results obtained in a large (for emulsion experiments) statistics – 362events of 9 Be2 peripheral fragmentation on H, CNO, AgBr. Theachieved accuracy of angular measurements not worse then 4.4 10 -3 rad.3) In peripheral interactions the 9 Be nuclei are dissociated practicallytotally through the 0 + and 2 + states of the 8 Be nucleus.4) The data obtained from 9 Be investigation can be employed for theestimation of the 8 Be role in more complicated N systems.15


Fragmentation of relativistic 14 N nuclei at 2.1 A GeVExperiment: N = 951 inelastic interaction (123.71 m); = 13.0 0.4 cm14NННeНeSingle- and two-chargedfragments identification from14N ws 3He+Husing the multiple Coulombscattering method16


3Не: 4 Не: 6 Не= 3:8:125% 14 N 8 Be+He+X8Be(0 + )6Li→ ЯФ 62, №8, с. 1461-1471, (1999)10B →ЯФ 66, №9, с. 1694-1698, (2003)*today at 12.30: T. Shchedrina «Clustering features of 14 N inrelativistic multifragmentation process».17


Fragmentation of relativistic 7 Be nuclei at 1.2 A GeVMeV1.622.17.128.021.05.618


Fragmentation of relativistic 8 B nuclei at 1.2 A GeV8B→Be+H8B→2He+H19


8B fragmentation channel (number of events)He+3H2He+HLi+2HLi+HeBe+H5H7Be: N. G. Peresadko et al., Phys.At.Nucl. 58, 1226 (2007).8B: R. Stanoeva et al., Phys.At.Nucl. 70, 1216 (2007).20


Fragmentation of relativistic 9 C nuclei at 1.2 A GeVThe charge topology distribution of the “white” starsZ fr5 4 4 3N Z = 11 2 - 1N Z = 2- - 1 1N ws11 16 1 233-2--313-4122-2221-6-19C B+H Be+2H Be+He Li+He+H Li+3H 3He He+4H 2He+2H 6H21


Double-charged fragments identification from 9 C ws 3 3 He using themultiple Coulomb scattering method9C22


Fully identified event of 9 C→3 3 He9CInteraction VertexFr 1 - 3 HeFr 2 - 3 HeFr 3 - 3 HeOpening angleΘ i,j mradP t ,MeVΣP t ,MeVP t* ,MeVε i,j* , radQ 23He ,MeVFr 1 56.0 466216 3.038 0.046Fr 2 55.0 154 760 111 3.034 8.786Fr 3 4.0 148 106 0.211 9.01723


Typical scales on emulsion plate & fragmentation of 32 Sevent of 32 S+Em at 200 A GeVhuman hair (30-50 m)emulsion layer24


n f ≠0E=200 A GeV (CERN/SPS, data of EMU01 collaboration)N=1558 inelastic interactions* of 32 S+Em (on 2758 tracks)The charge topology distribution of the 32 S+Em at 200 A GeVΣZ frZ fr(ns≠0) Nn b =0, n g =0≥3 2 1Nn b ≠0, n g ≠016 2 1 - 7 1016 2 2 - 11(ns=0)16 2 - - 6 1416 3 - - 1 -16 0 0 16 - 816 0 4 8 - 1816 0 5 6 - 2*A.A. Moiseenko and V.R. Sarkisyan, Yerevan Physics Institute, Yerevan,Armenia2nHe+mH25


Concluding remarksDue to a record space resolution the emulsion technique provides uniqueentirety in studying of light nuclei, especially, neutron-deficient ones.In presented talk, we give the prospects and results of the study of 7,9 Be , 8 B,9C and 14 N nuclei, fragmentation with a few A GeV energy which are obtainedwith the use of a part of the material analyzed.Providing the 3D observation of narrow dissociation vertices this classicaltechnique gives novel possibilities of moving toward more and morecomplicated nuclear systems. Therefore this technique deserves upgrade,without changes in its detection basics, with the aim to speed up the microscopescanning for rather rare events of peripheral dissociation.The presented observations serve as an illustration of prospects of theNuclotron for nuclear physics and astrophysics researches.26


http://becquerel.jinr.ru/27

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